The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Referring now to FIG. 1A, a power supply 5 supplies power to an electrical or an electronic device, which is generally called a load 20. A voltage regulator circuit (voltage regulator) 8 in the power supply 5 regulates an output voltage of the power supply 5. The voltage regulator 8 maintains the output voltage of the power supply 5 substantially constant although a supply voltage to the power supply 5 may vary within a predetermined range. Additionally, the voltage regulator 8 supplies a load current.
Voltage regulators use various topologies to regulate the output voltage. Referring now to FIG. 1B, a Buck-type voltage regulator (hereinafter a regulator) 10 uses a voltage hysteresis topology. Thus, the regulator 10 may be called a voltage hysteresis regulator. The regulator 10 regulates an output voltage Vout supplied to the load 20.
The regulator 10 comprises an error comparator 12, a Buck switch SW 14 (hereinafter switch 14), and a feedback circuit 16 that includes resistors RF1 and RF2. The feedback circuit 16 feeds back Vout to the error comparator 12. The error comparator 12 utilizes a voltage hysteresis and compares Vout to a reference voltage VREF.
Specifically, Vout is regulated by turning the switch 14 on or off when Vout varies between first and second threshold voltages. When Vout decreases to a value less than the first threshold voltage, an output of the error comparator 12 becomes high, and the switch 14 is turned on. An inductor current flows through an inductor L and charges an output capacitor C causing Vout to increase. The switch 14 remains on until Vout increases to a value greater than the second threshold voltage.
When Vout exceeds the second threshold voltage, the output of the error comparator 12 becomes low, and the switch 14 is turned off. The output capacitor C discharges, and Vout decreases. The switch 14 remains off until Vout decreases to a value less than the first threshold voltage, and the cycle repeats.
In addition to charging the output capacitor C, the inductor current supplies a load current to the load 20. Thus, the inductor current may be typically higher than the load current. Particularly, a peak value of the inductor current (i.e., a peak inductor current) may be high.
High values of peak inductor current may be disadvantageous. For example, to support high peak inductor currents, inductors with high saturation current ratings may be required. Additionally, high peak inductor currents may cause ripple in the load current. Consequently, current sensing and current limiting circuits may be required to reduce ripple in the load current.
Finally, using voltage hysteresis to regulate Vout slows a response time of the regulator 10. Slow response times may cause large overshoots and undershoots in Vout. Consequently, output capacitors having high capacitance values may be required to reduce the overshoots and undershoots in Vout.